Nhiều giao thức truy cập đối với truyền thông di động P5

... expanding on a paper from 1976 [244], he provided expressions for the variance in direct-sequence CDMA (DS/CDMA) systems, with random coding and BPSK modulation, as a function of the spreading ... Coding in CDMA According to Lee, coding is always beneficial and sometimes crucial in CDMA applica- tions [6]. Results reported in References [137,247,250,251] confirm this statement 7 . In digital .....

Ngày tải lên: 28/10/2013, 23:15

... usually distinguished. These are the pathloss, slow fading or shadowing, and fast fading or multi- path fading. The pathloss describes the average signal attenuation as a function of the distance ... GPRS, discrimination between the access delay performance experienced by different services is possible through computation of different permission probabilities for contending terminals accordin...

Ngày tải lên: 20/10/2013, 18:15

... standardisation of the UTRA FDD and TDD modes from ETSI (with UTRA now standing for universal terrestrial radio access rather than UMTS terrestrial radio access). Apart from ETSI and Japanese bodies, ... co-ordination is a different matter; a GSM- based cordless telephony system is a part of the GSM evolution story. As far as efficient use of the radio spectrum is concerned, refer to the discu...

Ngày tải lên: 20/10/2013, 18:15

... can readily be split into the sub-problems of: (a) providing a basic multiple access scheme such as frequency-division multiple access (FDMA), time-division multiple access (TDMA) or code-division ... layer, as indicated in Figure 3.1. In a mobile communications system, however, the transmission medium is the error prone radio channel, a medium subject to shadowing and fast fading. Designing...

Ngày tải lên: 24/10/2013, 16:15

... symbols, each symbol corresponding to a two-way transmission distance of approximately 1100 m. The maximum two-way transmission distance is 70 km, hence the maximum cell radius 35 km. Accounting for ... frequency hopping is a different matter, as discussed in more detail in Subsection 4.6.5. According to Reference [105], the main advantages of this feature are two-fold. Firstly, diversity on...

Ngày tải lên: 24/10/2013, 16:15

... possible. 6.2.3.2 Differences in the Random-Coding Case There are subtle differences in the contention procedure for the ‘pure’ random-coding case. Since no code-slots are discriminated, the ... contention mode between individual cycles. 6.3 MD PRMA with Time-Division Duplexing 6.3.1 Approaches to Time-Division Duplexing There are two fundamental approaches to providing time-division duplexin...

Ngày tải lên: 28/10/2013, 23:15

... generated by contending users. Only voice traffic is considered. We are investigating an interference- limited scenario, where code-slots are not distinguished, and random coding is assumed instead, ... scheduling. While we still believe that it will be rather difficult to exceed M x with any other distribution than this minimum-variance distribution for the typical P pe [k] curves found in Cha...

Ngày tải lên: 07/11/2013, 21:15

... scheme (assuming immediate acknowledgement); • the added traffic in the case of interleaving (I/L) due to dedicated request bursts and on average two additional bursts per voice spurt due to rounding up the ... performance of this protocol are discussed in Reference [37]. 2 This problem did not arise in Chapter 7, since a terminal, while holding a reservation in a certain time-slot, did not re...

Ngày tải lên: 07/11/2013, 21:15

... stack-based algorithms have the disadvantage of requiring immediate (although normally only binary) acknowl- edgements to work properly, which, as discussed at length earlier, is difficult to achieve in ... scheduled according to the QoS requirements of the different services considered. Alternatively, a single class of C-slots is provided, but access to these slots is controlled individually...

Ngày tải lên: 07/11/2013, 21:15

... categorised as either dedicated or common physical channels. 10.2.2.1 Dedicated Physical Channels All dedicated physical channels feature a radio frame length of 10 ms, with each frame subdivided into 15 ... acquisition Indicators (API) responding to CPCH access preambles. • The CPCH Collision Detection/Channel Assignment Indicator CHannel (CD/CA-ICH) carrying either Collision Detection Indic...

Ngày tải lên: 15/12/2013, 06:15